Re: Air pressure for F10
Ahaha well I took it as a challenge. I actually fine-tuned my calculation method. :thinking:
I did a research and found that the tyre contact area is usually ellipsoid in nature and research has shown that the contact height is approximately a 1.6 ellipsoid of the stock tyres (i.e. width 225).
So, re-calculate with my "new method". Call me keysiao if you want...
Max front axle load = 980 kg
Max rear axle load = 1,170 kg
Now we calculate the load per tyre. Remember, two tyres per axle unless you’re a truck or drive something not from planet earth.
Front tyre load = 980 / 2 = 490 kg = 1,080 pounds
Rear tyre load = 1170 / 2 = 585 kg = 1,290 pounds
Now we need to calculate the tyre contact patch:
Front:
Contact Width = Width of Tyre = 245 mm = 9.65 inch
Contact Height = Width of Stock Tyre / 1.6 = 8.86 / 1.6 = 5.54 inch
Contact Area = Pi x (Width/2) x (Height/2) = 3.142 x 4.83 x 2.77 = 42 square inches
Rear:
Contact Width = Width of Tyre = 285 mm = 11.22 inch
Contact Height = Width of Stock Tyre / 1.6 = 8.86 / 1.6 = 5.54 inch
Contact Area = Pi x (Width/2) x (Height/2) = 3.142 x 5.61 x 2.77 = 49 square inches
And we marry the load and contact patch together:
Front tyre pressure = Load / Contact Area = 1,080/ 45.7 = 26 psi or 180kpa
Rear tyre pressure = Load / Contact Area = 1,290 / 61.9 = 26 psi or 180kpa
BMW tyre ratings overinflated? It might be due the camber, especially the rears. :thinking:
Anyway I found this:
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=58
So to decrease oversteer (for our RWD)
Front tyre pressure = lower
Rear tyre pressure = higher
Front tyre section = smaller
Rear tyre section = larger
